An adaptive distance and speed control system is described in the publication “Adaptive Cruise Control System—Aspects and Development Trends,” SAE paper 961010 published at the SAE International Congress and Exposition, Detroit, Feb. 26-29, 1996. In this system, radar waves are emitted and partial waves reflected by objects are received. The relative position, relative speed, and distance of objects from the host vehicle are determined from the received signals and a power-determining final control element of an internal combustion engine and/or the deceleration devices of the vehicle are triggered as a function of these determinations. If the radar sensor does not detect a lead vehicle, the host vehicle is accelerated to a set intended speed and kept at that speed. If the radar sensor detects lead vehicles, the system switches from the speed control described above to distance regulation and the host vehicle follows the lead vehicle at a constant distance at the same speed as the lead vehicle.
German Published Patent Application No. 199 58 520 describes a speed control system for a motor vehicle which regulates the driving speed of the vehicle not only above a certain minimum speed but also at speeds below a predetermined limiting speed down to vehicle standstill. Automatic moving of the vehicle may be accomplished by detection of the traffic situation by a distance sensor if the driver has responded to a corresponding moving message. The moving message is effective for a predetermined limiting time, but it may also be repeated as an alternative. However, in any traffic situation, the driver has the opportunity to override the speed control by operating the accelerator pedal or the brake pedal.